The present invention relates to a grinding wheel for surface cutting of workpieces.
U.S. Pat. No. 3,343,306 discloses a grinding wheel having an annular abrasive lining arranged in a plane. Annular carrier sheets are screwed on an annular carrier wheel, the sheets holding a plurality of concentrically arranged rectangular portions for the abrasive lining. The sides of the segments facing each other are straight, while the peripheral sides each are circularly curved. Grooves for passing a cooling fluid are provided between the portions and the individual rings.
The shape of a grinding wheel of this type or, respectively, of its grinding surface is substantially defined by its inner and outer diameter which have to be selected according to the desired application (grinding wheel geometry). For example, three rings each including grinding portions are provided for the grinding surface of the known grinding wheel referred to. With a view to shaping the grinding portions, this means that three sets of differently dimensioned portions are required. When the inner and/or outer dimensions are changed, new sets of grinding portions are required. Thus, each grinding wheel geometry requires individual sets of grinding portions resulting in a substantial expenditure in manufacturing and storing.
Referring to the prior art grinding wheel, the grinding portions and rings are arranged in a distance from each other for passing a cooling fluid therebetween. The annular grooves prevent overlapping in the peripheral direction such that the shape of the annular groove may be reproduced on the workpiece which is not desirable.
The known grinding wheel is further affected by a geometry in which the distances or grooves between the grinding portions are initially reflected. The grooves cannot be changed for a predetermined geometry and corresponding dimensions of the portions. The width of the grooves between the portions should be selected as small as possible for relatively small workpieces. In other cases a larger width is desired. Thus the known grinding wheel may be used only for workpieces having a certain size.
U.S. Pat. No. 4,918,872 as well as U.S. Pat. No. 5,060,424 disclose a grinding wheel having a lining which is composed of trapezoidal portions which are arranged in sectors. Grooves are provided between the portions and between the individual sectors. The grooves between the grinding portions arranged in a sector extend approximately parallel and along a chord. Thus the danger of a lacking overlap when performing a peripheral and/or tangential forward feed is avoided. The radial extension of the grooves between the sectors, however, results in a fast draining of the cooling fluid which is not desired.
Still further, each grinding portion in a sector has necessarily a different contour. Accordingly, as many sets of grinding portions are required as grinding portions are provided in the sectors. Furthermore, a change of the grinding wheel geometry requires differently shaped sets of grinding portions so that for a predetermined number of differently dimensioned working surfaces, a correspondingly large number of differently shaped portions must be manufactured. Since the portions are mostly produced by means of molds, a correspondingly high number of different molds is required.
The grinding portions disclosed in the references referred to necessarily include acute angles. When portions of this type are produced e.g. by a sintering or ceramic burning process as commonly conventional, there is the danger that tensions are created in particular in the area of the acute angles which might result in fractures when the portions are subsequently handled or ground what might involve great dangers to workmen, for example. Acute angles further exhibit the disadvantage that the steel mold required for briquetting possibly cannot be uniformly filled. After the molding process, a varying hardness of the grinding portions must be expected. Furthermore, it is difficult or even impossible to check grinding portions within the region of acute angles for hardness and density as fractures may easily occur. Still further, acute angle grinding portions are subjected to damages when automatically applied. They suffer from a varying heating up during machining and exhibit a non-uniform shrinking behaviour when being manufactured.